Abstract:
In this research, natural rubber was reinforced with cadanol-formaldehyde resin prepared from cashew nut shell liquid. Cardanol-formaldehyde resins both resole and novolak were synthesized from cardanol which extracted from cashew nut shell. These were done via a condensation polymerization of cardanol and formaldehyde in the presence of base and acid catalysts. CF-resole with highest yield of 75.37% was prepared by using a molar ratio of 2.0 formaldehyde/cardanol at pH 8.0 and 90 degree Celsius for 8 h. CF-novolak with highest yield of 79.68% was prepared by using a molar ratio of 0.8 formaldehyde/cardanol at pH 2.2 with 100 degree Celsius for 7 h. Spectroscopic techniques, FT-IR and (superscript 13]C NMR were employed to characterize the chemical structure of the obtained cardanol-formaldehyde rasins. The resins were found to be compatible with natural rubber in various formulations. The cured behavior of natural rubber blended with either the CF resole or novolak was investigated. It was found that the cured behaviors of CF-resole and CF-novolak samples were quite different, reflecting differences in chemical reactivities. Furthermore, the incorporation of cardanol-formaldehyde resins into natural rubber gave significant improvements in mechanical properties such as hardness, tensile strength, modulus at 100% and 300% elongation and abrasion resistance. However, elongation at break and compression set of blends were decreased as expected.